Method of extracting mercury from cinnabar ore



Patented June 25, 1929.

UNITED STATES FRANK M. SCHAD, OF NEW YORK, N. Y.

METHOD OF EXTRACT ING MERCURY FROM CINNABAR ORE.

N Drawing.

The present invention relates, as indicated, to a new and improved method of extracting mercury from cinnabar ore, The principal object of the invention is the provision of a process for the above purpose which shall avoid the expense of the methods now in general use and which shall afford a convenient and economical process of extracting mercury chemically and in a wet way from low grade cinnabar ore with a recovery of 90 per cent or better of the mercury content of the orc.

To the accomplishment of the foregoing and related ends said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims.

The following description sets forth in detail certain steps embodying the invention, such disclosed steps constituting, however, but one of the various ways in which the principle of the invention may be used.

\Vhile it is known that black sulphide of mercury dissolves readily in a solution of an alkali sulphide, and that red sulphide of mercury is rapidly broken up and partially dissolved in a mixture of caustic soda and sulphide of soda solution, it has not been found commercially advantageous to employ these reagents for various reasons. It is impossible to rapidly filter and wash the residue of such a process and there is a considerable loss of sodium sulphide through the formation of soluble and insoluble heavy metal sulphides which are present as impurities in all ores. There is also in such a process a loss of caustic soda through its action on various siliceous rock constituents in the ore and through the absorption of carbonic acid. My improved process avoids the use of caustic soda and provides a rapid and economical process for the extraction of mercury. It consists, briefly stated, in first pulverizing cinnabar ore and working it into a thin paste with water and then reacting upon it with alkali or alkaline earth sulphides and alkali or alkaline earth sulfhydrates to produce a double water soluble sulphide which may beseparated from the solution by filtration; then the mercury is either removed by amalgamation and sublimation, or it may be removed by the addition of an acid to liberate black sulphide of mercury, which may then be furnaced under suit- Application filed March 11, 1926.

Serial No. 94,045.

able conditions and the volatilized mercury condensed and collected.

The first step in my improved process is to pulverize the cinnabar ore, which should be crushed and pulverized until it Will pass through a relatively fine screen, say at least mesh. The fineness of the crushed ore will affect the speed and completeness of the reactions of the further steps of the process, and 1t is therefore desirable to pulverize the ore to as fine a degree as is practical. It may in some cases be necessary to preliminarily treat the crushed ore or' powder to eliminate the ma or portion of certain impurities, such as iron hydrates and other iron compounds, sul phldes and other'compounds of other heavy metals, and the greater bulk of clay or min eral mixtures, this preliminary treatment, however, forming no part of the present process.

The finely crushed cinnabar ore or the concentrated cinnabar resulting from the prellminary purifying process is next mixed with a sufiicient amount of water to form a thin paste. To this paste is added one of the following solutions 1. A solution containing an alkaline earth metal sulphide and an alkali metal sulfhydrate, as for example, a solution of barium sulphide and sodium sulfhydrate, which. may be prepared from barium sulphide and sodium bicarbonate. The reaction occurring is represented by the following equation:

4BaS ZNaHCQ,

2BaS QNaSH 2BaCO 2. A solution containing an alkaline earth metal sulphide and an alkaline earth metal sulfhydrate, as for example, calcium or barium sulphide and calcium or barium sulfhydrate. This solution may be obtained as the product of the reaction of an acid, such as sulphuric acid, upon an alkaline earth metal sulphide, as calcium sulphide, and the reaction which takes place may be represented by the following equations:

CaS H SO CaSO, +H S.

2CaS+H S=CaS Ca (SH) 3. A solution containing an alkali sulphide In the latter case sodium carbonate is produced and may interfere with the proper solvent action ofthe reagent, and therefore the sodium carbonate formed may be removed by the addition of a suitable alkaline earth metal.

compound.

I have found that by using mixtures of sulphides and sulfhydrates of alkaline earth metals, or mixtures of sulphides of alkaline earth metals with sulfhydrates of alkali metals foreign impurities are only'slightly acted upon and the Cinnabar ore is quickly dissolved. If the cinnabar ore, however, is relatively free from other metal impurities hav- 1 ing an affinity for sulphur, such as antimony or arsenic compounds, or compounds of iron, then I prefer to employ the solution numbered above, which contains sulplnde and sulf hydrate of sodium, since I have found this mixture to dissolve cinnabar very quickly, especially when the solution 1s warm. In general, the reaction of the solutions named completed within 24 hours and at ordinary temperatures. The speed of reaction may be increased by slightly warming the m1xture and by maintaining it in agitated condition.

Themercury sulphide in the ore is dissolved to a double water-soluble sulphide, which 1s probably represented by the formulae:

BaSNa SHgS, or CaSNa Sl-lgS, or CaSHgS, or Nafil-lgS; i

The reactions which occur may be represented by the following equations:

1. QBaS +2NaSl-l HgS insna si-i si sa sir (a) QNaSH -l- I-IgS Na SHgS H 8,

(6) Na i? -l- H 8 QNaSH.

After the completion of the reaction the double sulphide of mercury may be separated "by filtration and may then be removed from the solution as an amalgam by the addition of a suitable metal such as zinc, aluminum or an alloy. The reaction may be represented by the following equations The amalgam is then distilled, causing the mercury to volatilize and it may be condensed and collected in the usual manner.

As an alternative method of recovering the mercury an acid oran acid salt may be added to the double sulphide solution in order to liberate black mercuric sulphide according to the following equation:

(13aS) .HgS +2HC1= Ba (SH) 2 BaCl l-lgS.

Uther modes of applying the principle of 'my invention may be employed instead of the one explained, change being made as regards the process her in disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

1 therefore particularly point out and distinctly claim as my invention 1. In a method of extract-in mercury from Cinnabar ore, the step which consists in reacting upon the finely divided ore with a solution of a sulphide and a sulphhydrate.

2. In a method of extracting mercury from cinnabar ore, the step which consists in reacting upon the finely divided ore with a sulpl'lideand a sulphhydrate in the presence of water thereby causing the formation of a double water soluble sulphide of mercury.

3. In a method of extracting mercury from cinnabur ore, the step which consists in reacting upon the finely divided ore with a sulphide and a sulphhydrate of; an alkali metal in the presence of water,' thereby causing the formation of a double water soluble sulphide of mercury.

4. In a method of extracting mercury from cinnabar ore, the steps which consist in finely with a sulphide of an alkaline earth metal and a sulphhydrate in the presence of water, and then amalgamating the double Water soluble sulphide of mercury formed.

5. In a method of extracting mercury from cinnabar ore, the steps which consists in finely pulverizing cinnabar ore, reacting upon it with a sulphide and a sulphhydrate in the presence of water, amalgamating the double water soluble sulphide of mercury formed, and then distilling and condensing the mercury from such amalgam.

6. In a method of extracting mercury from cinnabar ore, the steps which consist in finely pulverizing cinnabar ore, reacting upon it with a sulphide of barium and a sulphhydrate in the presence of water, and then reacting upon the double water soluble sulphide of mercury formed with an acid to produce mercuric sulphide.

7. In a method of extracting mercury from cinnabar ore, the step which consists in reacting upon the finely divided ore with a sulphide of barium and a sulphhydrate of an alkali metal in the presence of water, thereby causing the formation of a double Water soluble sulphide of mercury.

8. In a method of extracting mercury from cinnabar ore, the step which consists in reacting upon the finely divided ore with a sulphide of barium and sulphhydrate of sodium in the presence of water, thereby causing the formation of a double water soluble sulphide of mercury.

Signed by me, this 5th day of March, 1926.

' FRANK M. SCHAD. 

